The present invention relates to is a modular manifold system which has been developed to mount directly to pressure transmitters of both coplanar and biplanar types.
It is known to provide five valve manifolds with an integral body having the shape of a rectangular prism. They are typically provided with two block valves for selectively blocking or opening the input of the high and low pressure process fluid into the manifold. The high and low pressure process fluid is directed to a transmitter from which the pressure differential is monitored and transmitted. Disposed within the same body is a pair of vent valves used when it is desired to flush the ducts of the manifold with a flushing fluid usually delivered from the high or from the low pressure duct to the transmitter. With the vent valves selectively open or closed, the flow of the flushing liquid is manipulated.
Flushing of the ducts of a manifold system is an important operation in maintaining the system operative and accurate. However, after a period of operation, the length of which depends on the nature of the process fluid and other conditions, flushing is no longer sufficient and rodding (mechanical scraping) of sediments off inside walls of the passageways is required where such sediments may be difficult or impossible to remove by flushing.
An object of the present invention is to advance pressure transmitter manifold systems by producing a manifold system which allows for improved serviceability, a reduction in the number of valves required to operate the manifold system, a reduction in the number of separate components required by existing systems, a reduction in the number of potential leak points, minimizes environmental and safety hazards by allowing for the capture of toxic fluids released either through flushing of the manifold system or venting of the manifold system, improved economy and improved transmitter accuracy and response.
During the operation of differential pressure measuring installations there may be a requirement to service the orifice taps, the manifold, the passages connecting the orifice taps and the manifold or the pressure transmitter.
With respect to the pressure transmitter there may be a requirement to calibrate, test and repair the instrument. In some cases the pressure transmitter is best serviced in the controlled environment of an instrument shop, rather than in field. To accomplish this the transmitter itself, or the transmitter manifold assembly, must be removed from the field installation. The present invention is modular in nature. This permits the process fluid supply manifold to remain in service, while the support block of the manifold system, that portion directly connected to the pressure transmitter, is removed from service. The process fluid can be blocked by the process fluid supply manifold which remains in place, thus eliminating the need to provide additional block valves or to entirely shut down the process fluid flow.
The support block of the manifold system, remains connected to the pressure transmitter. This maintains the seal integrity between the pressure transmitters and the manifold, which, as some transmitter manufacturers recommend, permits precise assembly procedures and rigorous testing for the seal connection and represents a significant advantage. This seal is delicate in nature and not easily remade under field conditions. It is best left undisturbed. In the case of coplanar type transmitters, the support block also protects the delicate process isolator foils while the pressure transmitter is removed from its' installation for calibration or repair. Calibration, testing and repairs to the pressure transmitter can be conveniently carried out under controlled shop conditions, rather than in the field, with the support block attached to the transmitter.
Existing modular manifold systems were all developed for the industry standard pressure sensor spacing of 2.125" and as such could not mount directly to coplanar type transmitters with pressure sensor spacings of 1.3". The existing systems required the use of adapter flanges or plates. The present invention eliminates the need for such adapter components, thereby reducing the number of components and potential leak points.
The connection between the process fluid supply manifold and the support block is made by two couplings. The couplings incorporate an easily remakeable seal, which is shielded and protected by the coupling itself. The couplings can be readily connected and disconnected under field conditions, numerous times, without requiring the sealing gaskets to be replaced. The couplings are robust and rigid to allow the entire manifold system to be self supporting.
Another aspect of the operation of pressure measuring installations is servicing the manifold system and the various connecting passages, especially the passages connecting the orifice taps to the manifold. The nature of certain process fluids is such that the internal passages, particularly at the orifice taps, may become clogged or plugged. The passages from the process fluid source to the pressure transmitter must be open and clear for the process fluid pressures to be accurately monitored. The present invention allows for the internal passages to be kept open and clear.
These passages are maintained by rodding. Rodding is an operational practice which involves pushing an appropriately sized rod through the passages to remove any clogs or debris. The support block, after it is isolated from the process by the block valves, is removed from the connecting couplings to allow access to the manifold passages through the process supply manifold. The connecting couplings have been designed to allow the easy attachment of a pressure retaining rodding tool. The rodding tool is then inserted through the coupling connectors and into the manifold passages. The passages can be rodded through the block valves and back to the orifice taps.
The known manifolds have the disadvantage that they cannot be rodded due to the complex, tortuous passageway of the conduits through the manifold. Prior art known to the present applicant includes U.S. Pat. No. 4,672,628 (Nimberger) which shows a pressure signal instrument and manifold having a modular structure. Viewed from the standpoint of the present invention, the transmitter is mounted on the manifold so that the rodding of the manifold would probably require removal of the transmitter exposing the inlet face to possible damage. The arrangement does not allow efficient and convenient flushing as it is not adapted to be quickly connected to a source of flushing liquid independent of the process fluid.
U.S. Pat. No. 4,938,246 (Conley et al.) shows that it is known to provide a rodding tool. U.S. Pat. No. 5,313,985 (Donner) shows that it is known to provide a modular assembly of manifolds.